1. Field of the Invention
The present invention relates to a neutral-point terminal device for a dynamoelectric machine for conductively bundling and connecting a plurality of neutral-point side wires of a polyphase winding in a polyphase dynamoelectric machine.
2. Description of the Related Art
There has recently been an extensive need for size reduction of dynamoelectric machines such as electric motors in the fields of transportation means including automotive vehicles or machine tools including industrial robots. For example, dynamoelectric machines having three-phase windings (polyphase windings) are used in electric vehicles including hybrid cars. In the electric vehicles, a capacity for provision of a dynamoelectric machine has been reduced with size reduction of the vehicle body. Accordingly, miniaturization in the dynamoelectric machine is an inevitable problem.
JP-A-2003-348780 discloses one of the aforesaid dynamoelectric machines, for example. The disclosed dynamoelectric machine comprises a rotor and a stator which further comprises a stator core and magnet wires wound on the stator core into three-phase windings. Neutral-point side wires of a three-phase winding to be Y-connected have respective distal ends which are combined together by a neutral-point terminal. The neutral-point terminal includes a metal sleeve into which neutral-point side wires of each phase winding are inserted into the neutral-point terminal in the state of a bundle. The metal sleeve is then pressurized thereby to be deformed such that the wire distal ends of the respective phases are conductively connected to the metal sleeve. An insulation cap is attached to the metal sleeve, so that a neutral-point terminal is completed. The neutral-point terminal device is generally disposed in an axially recessed portion (useless space) of a coil end of the stator winding protruding from both axial sides of the stator core, namely, a valley.
In order that the above-noted need for miniaturization may be satisfied, it is effective for miniaturization of the whole dynamoelectric machine to shape coil ends of the three-phase windings so that an axial dimension is reduced. For this purpose, axial pressure is usually applied by a shaping jig to coil ends of the stator winding protruding from both sides of the stator core. As a result, the coil ends are spread radially outward with respect to the stator core, whereby a shaping step reducing the axial dimension is carried out. Subsequently, a varnish insulating treatment is applied to the dynamoelectric machine. In the shaping step, the shaping jig applies an external force to the neutral-point terminal, so that an external force is applied by the shaping jig to the neutral-point terminal. As a result, the neutral-point terminal is pressed against a surface of each coil end and moved along the surface of each coil end.
In the conventional neutral-point terminal, the bundled neutral-point side wire distal ends are inserted through the metal sleeve, and the distal ends are sharpened as the result of wire cutting. The external force the shaping jig applies to the neutral-point terminal causes the sharp edges to break through the insulating cap. As a result, insulation failure occurs and in a worst case, an enamel layer on the surface of the magnet wire is stripped off such that short circuit would occur.